Most wells drilled have some form of control of deflection, in the lateral direction, of the progressing drill head. A deliberate departure from a vertical direction is usually called directional drilling. The art of directional drilling has evolved to provide steering tools that enable drillers to observe at the surface indications of rotational orientation taking place down hole. Tools to deflect the progressing drill head from the existing well centerline can be simple but, if they are simple, they require rotational orientation and control of that orientation.
On a conventional drill string the rotational orientation of the down hole assembly may be done by manipulation of the drill string at the surface. If the drill string cannot be rotated, coiled pipe strings for example, the down hole assembly may need to be rotated relative to the drill string. There are other reasons to rotate one portion of the down hole assembly relative to another.
It is desirable for the driller to be able to rotate part of the down hole drilling assembly relative to another by actions taken at the surface in the form of selective manipulation of conventional drilling fluid flow controls.
It is therefore an object of this invention to provide apparatus to be part of the down hole drilling assembly that will respond to repeated increase and decrease of drilling fluid flow to progressively rotate drill string components below the apparatus relative to the drill string above the apparatus.
It is yet another object of this invention to provide apparatus that will resist the flow of drilling fluid and to utilize the flow related resistance to rotate a portion of the down hole assembly relative to another portion of the drill string a preselected amount each time the drilling fluid flow is changed between preselected amounts and to lock the rotating elements together when the drilling fluid flow is increased an additional preselected amount.
These and other objects, advantages, features of this invention will be apparent to those skilled in the art from a consideration of this specification, including the attached claims and appended drawings.